Cardiac arrest and cardiopulmonary resuscitation (CPR) are followed by coma and early death in up to 50% of cases, and in permanent brain damage in 20-40% of survivors. In 1977-79 we initiated the first and still only randomized clinical outcome study of CPR, the Brain Resuscitation Clinical Trial (BRCT). BRCT I (1979-83), evaluated the brain damage ameliorating effect of thiopental. No beneficial effect was found. Promising new experimental brain resuscitation therapies are now being pursued. Recent animal studies have demonstrated that calcium entry blockers can prevent or ameliorate postischemic cerebral hypoperfusion, protect against ischemic damage of myocardium and brain, and improve outcome after temporary complete global cerebral ischemia (cardiac arrest). BRCT II (1983-89) is currently evaluating, in 25 hospitals of 8 countries, the brain damage ameliorating effect of lidoflazine, an experimental calcium entry blocker, using a similar methodology as used in BRCT I. Of the required 500 cases, 200 have been entered. The goals of this study are: (1) to determine the ability of lidoflazine, started at 0- 30 min after of restoration of adequate spontaneous circulation (and repeated at 8 h and 16 h if the patient remains unresponsive) to ameliorate brain damage; (2) to identify complications of the therapy; and (3) to study neurologic and overall recovery and outcome during 6 mo follow-up. Most study patients have pre- hospital sudden cardiac deaths. They are entered if they remain comatose after restoration of spontaneous normotension. They are then randomly assigned to blinded i.v. infusion of lidoflazine or placebo. Both treatment groups receive the same standard life support. Using methods of evaluation, data collection, management and analyses adapted from BRCT I, we are comparing mortality, morbidity, neuropsychologic disability and quality of life during 6 months of follow-up, between control and treatment groups. Risk, benefit, balance of variables between groups, and adherence to protocols are continually monitored. Data will also be analyzed to answer many epidemiologic and clinical questions, as well as to search for accurate early predictors of outcome.